This application claims the benefit of Korean Patent Application No. 2001-85316, filed Dec. 26, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling a supplying amount of toner, and more particularly, to an apparatus for and a method of accurately controlling a mixing rate of toner and a carrier in accordance with an amount of printing data.
2. Description of the Related Art
A conventional image recording apparatus, such as a laser printer, a printer having a LPH (LED Print Head), or a PP (Plain Paper) facsimile uses an electrophotography developing method.
There are two types of developing methods to allow toner to stick to an electrostatic latent image formed on a photosensitive medium: a one ingredient developing method and a two ingredient developing method. The one ingredient developing method uses the toner only as a one ingredient developing agent, and the two ingredient developing method uses mixed toner and a carrier as a two ingredients developing agent. The image recording apparatus using the electrophotography developing method employs the two ingredients developing method. In the two ingredients developing method, the toner and the carrier are mixed in a predetermined proportion to form the two ingredients developing agent and to send the toner to the electrostatic latent image of the photosensitive medium. Hereinafter, the two ingredients developing agent having mixed toner and the carrier in the predetermined proportion will be referred to as a developing agent. The carrier is a medium to cause the toner to stick to the electrostatic latent image of the photosensitive medium. Ferrous ferrite can be used as the carrier.
It is very important to control a toner density to obtain a good quality of a printing image in the two ingredients developing method unlike the one ingredient developing method. While an amount of the toner is controlled because only the toner is used in the one ingredient developing method, each proportion of the toner and the carrier, in other words, the toner density should be controlled in the two ingredient developing method. Hereinafter, the proportion of the toner and the carrier will be referred to as the toner density.
To maintain the quality of the printing image, it is required to control the toner density accurately. The toner density can be controlled to maintain the proportion of the toner and the carrier constantly. Several methods have been used to control the toner density. For example, a method of compensating for the amount of the toner as much as a change of the toner density which is determined using a signal of a toner sensor in a CPU of the image recording apparatus, is used to control the toner density.
FIG. 1 is a block diagram showing a device controlling the toner density. As shown in FIG. 1, a controller (CPU) 10 calculates a value for controlling a toner supply motor by detecting a variation of the toner density in accordance with a signal input from a toner sensor 20 and controls a supply amount of the toner by driving a toner supply motor driving unit 40 in response to the toner supply motor controlling value.
The toner supply motor controlling value is calculated at the controller 10 by using a difference between a toner density set-up value set up to improve the printing quality and a toner density detection value actually detected by the toner sensor 20. The controller 10 calculates the toner supply motor controlling value to meet the set up toner density and controls the supply amount of the toner by driving the toner supply motor driving unit 40 in response to the toner supply motor controlling value. The toner supply motor controlling value can be set up when the toner supply motor driving unit 40 is turned on or a voltage is supplied to the toner supply motor. The toner supply motor controlling value is calculated by an operational constant of the toner density set-up value stored in a memory 30 when the image recording apparatus is manufactured, and by the toner density detection value input from the toner sensor 20.
FIG. 2 is a flow chart showing a conventional method of controlling the toner density. As shown in FIG. 2, the controller 10 reads the operational constant of the toner density set-up value stored in the memory 30 and a toner controlling value in operation S10. Then, the controller 10 reads the toner density detection value in operation S20, and calculates a difference xe2x80x98exe2x80x99 between the toner density set-up value read in the operation S10 and the toner density detection value read in the operation S20 in operation S30. Next, the controller 10 calculates the toner supply motor controlling value xe2x80x98Uxe2x80x99 by using the operational constant read in the operation S10 and the difference xe2x80x98exe2x80x99 of the toner density set-up value and the toner density detection value calculated in the operation S30 in operation S40. The controller 10 drives the toner supply motor according to the toner supply motor controlling value xe2x80x98Uxe2x80x99 in operation S50. Each of the above operations S30, S40, S50 is repeated (see operation S60) after returning to the operation S20 until a printing operation is completed. The above conventional method controls the toner density by considering only the toner density detection value of the toner sensor and the operational constant.
The toner density should be changed in accordance with a consumed amount of the toner for a predetermined duration, and the consumed amount of the toner should be changed in accordance with printing information (data) about the printing image. When the printing information is a 5% coverage of a sheet of paper, a ratio of the number of dots of the printing information and the number of the entire dots that is printable on one page of the sheet is approximately 5%. Therefore, when the printing information is the 5% coverage, it can be said that the amount of the toner used for printing the printing image on the page of the sheet is approximately 5%. When the printing information is a 100% coverage, the page of the sheet would be printed all black. When a high density background color is used in the printing information, the printing coverage would be 50 to 70%.
In a printing operation for a printing object that requires relatively less printing coverage, there is a narrow difference between the toner density set-up value and the toner density detection value due to relatively small consumption of the toner. For a printing object that requires a wide printing coverage, however, the difference between the toner density set-up value and the toner density detection value becomes wider. For example, when documents including a small amount of letters and documents including a dark colored photograph are printed in turn, a variation of the printing coverage becomes greater. As the variation of the printing coverage increases, there is a great change in the toner supply. Further, if the supply amount of the toner increases more than the toner density set-up value, the toner is scattered. There is a wide difference in the toner consumption per unit time between a case where the toner consumption is 5% and another case where the printing object has a density almost black. Accordingly, there needs to be control of the printing operation of compensating for the difference.
However, the conventional toner density controlling apparatus and method uses a regular operational constant stored in the memory when calculating the toner supply motor (amount) controlling value. In other words, the toner supply motor controlling value is decided by considering only the toner density detection value detected by the toner sensor to the change of the consumed amount of the toner. Therefore, a period of time is required to adjust to the toner density set-up value, and there is a difficulty in controlling the toner density accurately since the toner amount is controlled with only the toner density detection value detected by the toner sensor without considering the printing coverage of the page of the sheet according to the printing information of the printing object.
The present invention has been made to overcome the above and other problems of the prior art. Accordingly, it is the object of the present invention to provide an apparatus and a method capable of controlling a toner density accurately in accordance with printing data.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
A toner density controlling apparatus according to an embodiment of the present invention to accomplish the above and other objects includes a memory to store a toner density set-up value and having an operational constant table having an operational constant (toner supply amount controlling value operating constant) corresponding to an amount of dots forming an image corresponding to printing data, a toner sensor detecting a toner density, a toner supply amount controlling unit, and a CPU deciding the operational constant in response to a signal of the printing data by using the operational constant table, calculating a controlling value of the toner supply amount controlling unit by using the operational constant, a toner density detection value output from the toner sensor, and the toner density set-up value stored in the memory, and controlling the toner supply amount controlling unit in response to the calculated controlling value.
A toner density controlling method to accomplish the above and other objects of the present invention controls the toner density by calculating the toner supply amount controlling value in response to the toner density set-up value and the toner density detection value by the toner sensor. The controlling value is calculated by changing a toner supply amount controlling value in response to the operational constant by an amount of toner required to print the image corresponding to the printing data.
The toner density controlling method according to another embodiment of the present invention includes reading the operational constant from the operational constant table corresponding to an amount of dots forming the image corresponding to the printing data, reading the toner density detection value detected by the toner sensor, deciding (selecting) the operational constant by receiving the signal in response to an amount of the printing data, calculating the toner supply amount controlling value by using the operational constant decided in the above operation, the toner density set-up value, and the toner density detection value, and driving the toner supply amount controlling unit in response to the toner supply amount controlling value calculated in the above operation.
The above operational constant table includes the operational constant and a toner supply amount controlling value operational expression set up by experiments in order to determine a consumption rate of the toner consumed in accordance with the amount of the dots to be printed to form the image corresponding to the printing data. The toner supply amount controlling value is obtained by calculating the amount of the dots constituting the printing data and deciding the toner supply amount controlling value operational expression in response to the amount of the dots and the operational constant of the operational constant table.
The toner supply amount controlling value is calculated by using an equation U=KPe+KIedt+KDde/dt. Here, xe2x80x98exe2x80x99 is a difference between the toner density set-up value and the toner density detection value, and KP, KI, and KD are the operational constants decided by using the operational constant table. The toner supply amount controlling value xe2x80x98Uxe2x80x99 is a period of time during which an electric current flows to a toner supply motor performing a printing operation.